Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

Line/W1.

rrnn STATES FFICEQ PATENT MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG. SlVI'lCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M U LTl PLE SWITCH BOARD.

SPECIFICATION forming part of Letters Patent No. 592,366, dated October 26, 1897.

Application filed July 26,1890- fierial No. 360,075. (No model.)

To ctZZ 1072,0712 it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the lines are singlecircuit lines grounded at their outer ends and normally grounded at the central office; and it consists in a system of testing the lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 represent sections of two multiple switchboards of the exchange to which the same lines are connected. Fig. 2 shows a diagram of the boards with the mainline apparatus and connections necessary to illustrate my invention. Fig. 3 shows a diagram of an operators cord system to be used in connection with the boards. Fig. 4 shows an operators test system to be used at the board. Fig. 5 shows a subscribers-station apparatus.

In Fig. 2, A is a sectional view of the switchboard shown in Fig. 1, and A is a sectional view of the switchboard shown in Fig. 1 each as indicated by the line 01 e.

I place as many boards in the central office as are found necessary or desirable in order to properly operate the exchange. On each board is a spring-jack or other suitable switch for each line. Each switch has a contactspring which normally connects with an insu lated contact-piece and is adapted to receive a loop-plug and, when a plug is inserted, to disconnect the spring from the contact-piece and connect the two contact-pieces of the plug with the spring and said insulated contact-piece, respectively. The switch is also adapted to receive a single-contact switchplug and, when a plug is inserted, to disconnect the spring from the contact-piece and connect the spring with the contact-piece of the plug.

In the construction of the switches as shown and as will hereinafter be described I prefer to have a contact-point electrically connected with the contact-piece and on which the spring normally bears, as there is less chance of poor connection when the spring bears on a point than when it bears on a surface adapted to be brought into connection with the plugcontacts.

I In Fig. 2, g g represent the springs of the different switches, 77. h the contact-points on which the springs normally bear, and jj the contact-pieces of the switches connected with the points h h. Z l are the switch-holes. a I) are the rubber strips on which the metal parts of the switches are mounted, as shown, and through the fronts of which are the switchholesl Z. The contact-pieces jj are so placed along one of the surfaces of the plug-holes as readily to form connection with one of the contact-pieces of the loop-plugs. The holes H are adapted to receive the switch-plugs shown in Fig. 3 and marked D D, and when a plug is inserted into a switch it raises the spring g from the contact-point h, andthe spring 9 and the contact-piece of the plug are in contact. These holes are also adapted to receive the loop-plug shown in Fig. 4, and when a plug is inserted into a hole it raises the spring of the switch from the contactpoint h, and the spring g and the contactpiece j of the switch are in contact with the two contact-pieces of the plug, respectively.

w and 0c are calling-annunciators, one for each of the lines shown. Each annunciator has a pair of contact-points normally (or when the annunciator does not indicate a call) in contact with each other, but which are separated by the annunciator while it indicates a call. The two contact-points of a pair are marked p and g, respectively. One of them, q, is a spring-contact, which is pressed by the annunciator-drop when the drop falls away from its corresponding contact-pointp. The contact-point p is represented as an angle-piece which passes over the spring (1 and is in contact with the spring when the spring is not actuated by the annunciator-drop.

Two lines are shown in the drawings, one marked line No. l and the other line No. 2. These lines are ordinary single-circuit lines grounded at their outer ends and having at the subscribers stations any usual and appropriate subscribers station apparatus.

ciator and the pair of contact-points of the annunciator to the common ground wire or The circuit of each connection of the lines. line shown may thus be traced in Fig. 2. In the operators cordsystem shown in Fig.

3, D D are the switch-plugs of a pair of cords, n n are the rubber insulations of the plugs, These conand 'm m are their contact-pieces. tact-pieces pass each to the bottom of its 0, which then connects it with the ground. Weights, as is usual, or similar devices may be used to bring the contact-pieces of the plugs into contact with the piece 0 and seplugs should be inserted so that the contactpiece on is in contact with the spring 9. The connections of the lines might have been reversed, so that the lines pass first to the contact-piece j of each of their switches, and in that case the plugs should be inserted in such aposition that their contact-pieces form connection with the pieces j of the switches. Y is the looping-in switch for the pair of cords shown. 7t is the calling-key, and r is a clearing-oiit annunciator. 25 is the operators telephone, and B is her calling generator or battery. The circuits are substantially as shown.

The operation of the system, in connection with the switchboards, will be apparent to those skilled in the art. It will readily be apparent that when a line is switched by the insertion of a plug into its switch the line is disconnected from its normal ground-wire at the central office and is connected into a circuit with the pair of cords. Only one pair of cords --is shown, but the connection of such other pairs with their accompanying apparatus as the operator may need will be apparent to those skilled in the art. To each pair of cords, With its plugs, belong a looping-in switch, a clearing-out annunciator, and a calling-key. One telephone and one calling-generator will answer for her system of cords.

In the operators test system shown in Fig.

4, T is a loop test-plug adapted to be inserted into any of the switches and, when inserted, to operate them as heretofore described, B is a test-battery, and S is a test receiving instrument. The instrument and battery are connected in a loop which terminates in the two contact-pieces of the plug. Each operator has one cord system and one test system and they are conveniently mounted and arranged for her work.

In the subscribers-station apparatus shown in Fig. 5 1 is the telephone-switch. 2 is the calling-generator. 3 is the signal-receiving bell. 4 is the'subscribers telephone. 5 is the These plugs are secondary, and 6 is the primary, of the induction-coil. 7 is the transmitter. '8 is the transmitter-battery. 9 is a resistance-coil of suitable resistance to operate as hereinafter described. These parts may be of usual forms of apparatus and are connected as shown or in other ways, so as to perform practically the operations required and the operations hereinatter described.

When the subscribers telephone is on its switch, the signal-receiving bell is in the circuit of the line, and the telephone, the secondary of the induction-coil, and the resistplug and are adapted to rest normally, or when the plug is not in use, on the metal piece 1 ance-coil are shunted by a wire of small resistance, so as to be practically out of the circuit. When the telephone is off the switch, the telephone, the secondary of the induc tion-coil, and the resistance-coil are in the circuit and the signal-bell is practically out of the circuit. The resistance of the telephone and secondary of the induction-coil com bined aggregate in well-constructed apparatus about four hundred ohms and the resistance of the signal-bell amounts to about one hundred ohms. The resistance switched into the circuit when the telephone is off its switch for use is therefore much greater than is the resistance in the circuit when the telephone is in its normal position on the switch. I utilize this diiterence in resistance in the operation of the test system as will hereinafter appear. If the diiterence in the resistance when the telephone is off its switch for use and when it is in its normal position on the switch is not sufficient to secure an easy adjustment of the test apparatus to the circuits, such additional resistance as is required maybe placed in the resistance-coil 9. Whether this artificial resistance is used, and its amount, if used, will depend on the apparatus and circuits to which the system may be applied.

The test receiving instruments and testbatteries should be so constructed and adjusted to each other and the circuits that the instrument will sound or respond when it and the battery are looped into the closed circuit of any single line and the subscribers telephone is not off its switch for use, but will not respond if the circuit is open at any point, or if the subscribers telephone is off its switch and the additional resistance at the subscribers station is included in the circuit, or the line is switched with another line and theresistance of two lines is in circuit with the test instrument and battery. This adjustment can be regulated as required by the addition of artificial resistances in the circuits. This construction and adjustment depend on the fact that an electromagnet may be readily made so as to operate when a battery and a cer-. tain resistance is in circuit with it and not to operate when the resistance is considerably larger. This operation can be obtained in different ways, dependent on the style of the justment of the retractile spring. These parts should be such that the electromagnet will be actuated when the test system is looped into the normal circuit of any line of the eX- change, but will not be actuated when the additional resistance is introduced. The resistance of the coils may be such as is necessary or desirable in order to obtain such an adjustment of the parts of the exchange system.

The operation of the test system is as follows: Then an operator desires to test a line, she places her test-plug into the switch of the line and by so doing disconnects the points g and h of the switch and connects them with the contact-pieces of the plug. It, then, the line is not switched at any board and the annunciator does not indicate a call and the subscribers telephone is on its switch, the test receiving instrument will sound or respond, indicating that the line is free to be switched to. If, however, the line not being switched the subscriber has sent in a call and the annunciator indicates the call or has taken his telephone from the switch for use, the instrument will not sound, as the line being open at the annunciator-points or the additional resistance in the circuit will prevent it from doing so. If, again, the line is switched at some board and the test is made in the cut-off portion of the line-that is, that portion which is between the switch used for switching and the office ground-the instrument will not sound, because the test-circuit is open at the pair of ,contact-points of the switch used for switching. If, again, the line is switched at any board with another line and the testis made in some switch between the one used for switching and the subscribers station, the instrument will not sound on account of the resistance of two lines being in the circuit in which the test receiving instrument and battery are included.

Then a test of a line is made and the test receiving instrument sounds, the operator knows that neither the line is switched for use nor the line-annunciator indicates a call, and when the instrument does not sound she knows that either the annunciator indicates a call, or the subscribers telephone is switched for use, or the line is switched for use and she will not connect the line with any other line. By this system a subscribers line is reserved to himself from the time he sends in his call or takes the telephone down for use.

In multiple-switchboard systems an operator to whom certain lines are assigned to answer frequently receives several calls at practically the same moment and it may re quire some time before she can switch to a certain line and answer its call. In systems in which the test depends only on the line being switched at some board another operator may in the meantime test the line and finding it to test free may switch it with an other line and cause annoyance and confusion to the subscriber. This cannot occur in this system of testing, because as soon as the sub scriber takes his telephone from its switch the line will test busy whether or not it is switched at the central office. Again, in systems of testing which depend only on the subscribers telephone being on or off its switch confusion frequently arises from the fact that asubscriber places his telephone on its switch when he is through conversation without sending in a clearing-out signal, and his line tests free and is connected to when it is already switched with another line; Lines in this condition are technically called tied up. This, again, cannot occur in this system, because the line will test busy until it is disconnected at the central office whether or not the subscribers telephone is on its switch. The system therefore combines the advantages and obviates the disadvantages of the two general systems of testing outlined above. Moreover, in this system the line tests busy as soon as the calling-generetor operates, and the annunciator indicates a call whether the subscriber may have taken down his telephone for use or have replaced it on its switch.

I claim as my invention and desire to secure by Letters Patent 1. In a telephone-exchange system, a telephone-line normally on closed circuit and an annunciator normally in the circuit of the line, having contact-points by which the circuit is open while the annunciator indicates a call, in combination with a subseribers-station apparatus having a telephone, a telephone-switch, resistances, contacts and con nections by which a greater resistance is included in the circuit of the line while the telephone is switched for use than while it is not thus switched, a test-loop containing a test receiving instrument and battery, andswitch apparatus by which such loop may be connected into the normally closed circuit of the line, the instrument and battery being so constructed that the instrument sounds when they are included in the circuit of the line and neither the telephone is switched for use nor the annunciator indicates a call and not to sound when either the telephone is thus switched or the annunciator thus indicates, substantially as set forth.

2. In a telephone-exchange system, a telephone line normally on closed circuit and an annunciator normally in the circuit of the line, having contact-points by which the circuit is open while the annunciator indicates a call, in combination with a subscribers-station apparatus having a telephone, a telephoneswitch, resistances, contacts and connections by which a greater resistance is included in the circuit of the line while the telephone is switched for use than while it is not thus switched, switching apparatus by which the line may be switched with anotherline, a testloop containing a test receiving instrument and battery, and switching apparatus by which such loop may be included in the normal circuit of the line, the instrument being so constructed and adjusted to the battery and circuits that it will sound or respond when connected into the circuit with the line and neither the telephone is switched nor the-line is switched nor the annunciator indicates a call, and not to sound when either the telephone or line is switched or the annunciator indicates a call, substantially as set forth.

3. In a telephone-exchange system, a telephone-line normally on closed circuit and an annunciator normally in the circuit of the line, having contact-points by which the circuit is open while the annunciator indicates a call,

in combination with a subscribers-station apparatus having a telephone, a telephoneswitch, resistances, contacts and connections by which a greater resistance is switched into the circuit of the line when the telephone is switched for use than when it is not thus switched, switching apparatus by which the line may be switched with another line, atest receiving instrument, switch apparatus by which the instrument may be included in the normal circuit of the line, and a battery in the normal circuit thereby established, the instrument being so constructed and adjusted to the battery that it sounds or responds when connected into the circuit with the line and neither the telephone nor the line is switched for use nor the annunciator indicates a call, and not to sound or respond when either the telephone or line is thus switched or the annunciator indicates a call, substantially as set forth.

4:. In a telephone exchange, system, telephone-lines grounded at their outer ends and multiple switchboards for the lines, each board containing a switch for each line, each switch having a pair of contact-points normally in contact, adapted to receive a switchplug and when the plugis inserted to have the contact-points separated and the contactpiece of the plug in contact with the line contact-point of the switch and with that only, and adapted to receive a loop test-plug and when the plug is inserted to have the contactpoints separated and connection made between them and the two contact-pieces of the plug, respectively, each line passing successively through the contact points of its switches, passing in its case to the line-point first and from the last switch to the ground, in combination with an annunciator in the circuit of each line, each annunciator having a pair of contact-points in the line-circuit normally closed but open while the annunciator indicates a call, a subscribers-station appa-- ratus for each line, containinga telephone, a telephone-switch, resistances, contacts and connections by which a greater resistance is included in the circuit while the telephone is switched for use than while it is not thus switched, a loop test-pl ug and a test receiving instrument and battery at each board, said instrument and battery being included in a loop the two ends of which terminate in the two contact-pieces of the plug, the instrument being so constructed and so adjusted to the battery and the circuits that it sounds or responds when the plug is inserted into a switch of any line and neither the subscribers telephone nor the line is switched for use nor the annunciator indicates a call and does not respond when either the telephone or the line is thus switched or the annunciator indicates a call, substantially as set forth.

In witness whereof I hereunto subscribe my name this 23d day of June, 1890.

MILO G. KELLOGG.

Witnesses:

EMIL ABENHEIM, O. STRIOH-CHAPELL. 

